Double-twist stranding or cabling machine

ABSTRACT

A double-twist stranding or cabling machine in which wires to be twisted pass through a hollow shaft to a pulley on a rotating arm to be twisted, then over a flexible transfer track to a second arm to be returned to a central take-up reel on a rocking cradle while being twisted again. The flexible transfer tracks can be formed by steel ropes which are pulley mounted and spring tensioned to extend from a flat state to a curved state during operation of the machine. This flexibility of the tracks avoids the undesirable bending stresses which affect prior art transfer tracks or arcs, which are relatively rigid and inflexible.

United States Patent [1 1 Sarracino DOUBLE-TWIST STRANDING OR CABLINGMACHINE [75] Inventor: Marcello Sarracino, Milan, Italy 211 Appl. No.2370,336

[30] Foreign Application Priority Data June 22, 1972 Italy 26026/72 [52]US. Cl 57/5852, 57/5865, 57/587 [51] Int. Cl D07b 3/10 [58] Field ofSearch 57/5849, 58.52, 58.54,

[56] References Cited UNITED STATES PATENTS 2,773,344 12/1956 Van Hook57/5865 X [451 May 28, 1974 2,921,429 1/1960 Haugwitz 57/58.? X3,142,952 8/1964 Krafft et al. 57/5852 X 3,309,857 3/1967 Haugwitz57/5852 X Primary ExaminerJohn Petrakes Attorney, Agent, or Firm-BrooksHaidt & Haffner [57] ABSTRACT A double-twist stranding or cablingmachine in which wires to be twisted pass through a hollow shaft to apulley on a rotating arm to be twisted, then over a flexible transfertrack to a second arm to be returned to a central take-up reel on arocking cradle while being twisted again. The flexible transfer trackscan be formed by steel ropes which are pulley mounted and springtensioned to extend from a flat state to a curved state during operationof the machine. This flexibility of the tracks avoids the undesirablebending stresses which affect prior art transfer tracks or arcs, whichare relatively rigid and inflexible.

8 Claims, 3 Drawing Figures PATENTEUMM 28 1974 m 2 or:

DOUBLE-TWIST STRANDING OR CABLING MACHINE BACKGROUND OF THE INVENTION 1.Field of the Invention The present invention relatesto ah improveddoubletwist stranding or cabling machine. More particularly the machineof the invention is especially, but not exclusively, suitable forstranding individual bare wires to obtain cords or strands as well asfor twisting or stranding insulated wires for the manufacture oftelephone or power cables.

2. Description of the Prior Art The most advanced double-twist strandingmachines heretofore used have employed a twisting unit having a pair ofaligned shafts, one of which shafts is hollow. Each of the alignedshafts of prior art twisting units carries an arm element arrangedperpendicularly to, and keyed to, the shaft. These arms can be shaped ascones or discs and are in spaced opposed positions, and tracks extendbetween the opposed arms for the transfer of wire from one arm to theother. The two shaft and arm assemblies rotate about the same axis at asynchronized speed. 1

The wires to be stranded pass through a central cavity of the hollowrotating shaft and are conveyed towards wire-guiding means situated onthe arm near the place where they emerge from the cavity in the shaft;at this point they are dragged into rotation along with the rotatingarm, and are thus subjected to a first twist. From the point at whichthe wires are first twisted, the wires are guided by appropriate meansto a transfer track which brings the wires which have already beensubjected to the firsttwist towards thefacing surface of the oppositearm where, by means of guiding means secured to this second arm andsymmetrical to those of the first arm, the wires are brought again tothe axis of the twisting unit to be subjected to a second twist and tobereturned to rectilinear motion. Then the wires are collected on a drum.Prior art machines of the above described type take-up" machines.

Stranding machines of a so-called outer take-up type are also known inwhich the wires to be-stranded follow a similar path, but in the reversedirection, from inside to outside the machine to be taken up outside thepositions of the arms as opposed to inside as in the inner take-up typeof machine.

Generally, the transfer tracks for transferring the wire from one arm tothe other are formed as arcs. In most cases, there are two such arcs,symmetrically arranged with respect to the longitudinal axis of themachine, which axis is also the axis of rotation of the twisting unit.In general, the arcs ,of prior art twisting units have a curved shapeapproximating a parabola, designed to comply with the requirement thatthe unit occupy the minimum space and also intended to generateacceptable stresses on the various components of the machine duringoperation. Arcs of various types are are called inner 2 the generallyinflexible arcs of the prior art can sometimes cause the arcs to break.

In order to ensure perfect reliability of a generally inflexible arc ofthe type described it would be necessary to form the arc with ageometrical configuration able to eliminate any bending stress under theaction of centrifugal forces, so that the only effective stress would bethat due to tension. Such a bending-stress-free configuration isdifficult to achieve in practice, since centrifugal forces acting on thearc in operation would have to be considered, and such forces are notuniform but, being directly proportional to the rotation radius, varyfrom point to point along the arc.

The present invention aims at obviating the above indicateddisadvantages by providing tracks for the transfer of the wires whichare perfectly flexible and which, in operation, spontaneously take onthe configuration required by the centrifugal forces involved, andtherefore operate under tension alone.

SUMMARY OF THE INVENTION The present invention relates to a double-twiststranding or cabling machine of the type in which the twisting unitcomprises at least a pair of shafts, at least one of which shafts ishollow. The shafts are aligned and each shaft carries an element shapedas a disc or arm perpendicular toand keyed to the shaft. The discshapedelements or arms are spaced apart from one another, in an opposedface-to-face relationship and are connected by at least one pair oftransfer tracks for the wire to be twisted. There are preferably twosuch transfer tracks, symmetrically situated with respect to the .axisofthe twisting unit. Means for transferring and guiding the wire areprovided on the shafts and on the disc-shaped elements or arms. Each ofthe transfer tracks comprises at least one flexible element which is Iable, under normal working conditions, to take on a configurationproportional at any point to the centrifugal forces involved. Eachtransfer track has elastic means for recovering and limiting its ownelongation.

The invention will be more fully understood by consideration of thefollowing detailed description of a pre-' ferredembodiment of theinvention, especially when read in conjunction with the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING The figures of the attached sheets ofdrawings represent by way of non-limiting example an embodiment of theinvention; more precisely:

FIG. 1 is a diagrammatical view of a preferred em- DETAILED DESCRIPTIONOF A PREFERRED EMBODIMENT The stranding orcabling machine illustrated inFIG. 1 is of the inner take-up" type and comprises supports 10 and 11,carrying a twisting unit generally indicated by the reference numeral12. The twisting unit 12 com- 3 prises two mutually aligned, rotatableshafts113 and 14. The shafts 13 and 14 are seatedrespectively in seats15 and 16 and are arranged to be driven by a driving system including abelt 17 for driving the shaft 13, a transmission shaft 18, and a belt 19for driving the shaft 14. Both belts 17 and 19' are operativelyconnected to the transmission shaft 18 to synchronize the speed of thetwo shafts 13 and 14.

Each of the shafts 13 and 14 carries an arm, keyed to theshaft forrotation therewith. 1n the preferred embodiment shown inthe drawing, theanus 20 and 21 of the shafts 13 and 14 respectivelyare formedasdiscshaped elements hereinafter referred to as discs," but the armscould be conically or otherwise shaped elements extending generallyperpendicular to the axis of rotation of the shaft.

Each of the shafts 13 and 14 also carries, mounted in proximity to itsdisc 20 or 21, a wire deflecting pulley 22 or 23, respectively. Groupsof pulleys 24, 25 and 26,

. 27 are mounted on the discs 20, 21, respectively, just within theperiphery of the discs 20,21 and in proximity to the ends of respectivetransfer tracks 28 and 29. The straightline configurations of the tracksindicated by the dashed lines 28 and 29 show the tracks in restposition. The curved configurations of. the tracks 28 and 29 shown insolid lines at 28a and29a indicate the elongation of said transfertracks in'response to centrif. u gal force during operation under normalworking conditions.

In the embodimentof the stranding-cabling machine of the invention shownin the drawing, the track 28 behaves in operation as a true transfertrack for carrying wires 30, which have been subjected to afirst twist.The other track 29 serves only to counterbalance the track 28 duringoperation, and carries no wire. The track 28 comprises two wire cablesor steel ropes 31 and 32 but could alternatively have but a single rope.The ropes 31 and 32 are stretched between the disc-shaped element 20 andthe element 21 andare carried bythe races of lateral pulleys of thepulley groups 24 and 26.'FIG. 2 of the drawing shows only the lateralpulleys 33 and 34 of the pulley group 26, but it will be understood thatthe arrangement of the pulleys of group 24 at the disc 20 can besimilar. The rope 31 is carried by the race of pulley 33 and the rope 32is carried by the race of pulley 31. One end of each of the ropes 3'1,32 can be secured directly to the outer face 44 of disc 20 and the otherend of each rope 31, 32 engages the outer face 45 of disc 21 as shown inFIG. 2, through an elastic extension and recovery mechanism for eachrope, namely the mechanism 47 for rope 31 and the mechanism 48 for rope32.

The extension and recovery mechanisms 47 and 48 for the steel ropes 31and 32 of the transfer track 28 allow the steel ropes to be extended toa limited decree to take on a curved configuration under tension inresponse to centrifugal forces resulting from rotation of the twistingunit 12 and also provide for recovery, i.e., shortening andstraightening of the transfer track 28 from the extended operatingposition (28a of FIG. 1) when the centrifugal forces decrease. I

The recovery mechanism 48 is a mirror symmetrical image of the mechanism47, so the mechanism 47 will be described with odd reference numbers andeven refments of the recovery unit 48.

The extension and recovery mechanism 47 (48) comprises a race pulley 35(36) pivoted about its center 37 (38). The rope 31 (32), whose terminalportion is secured in said race, is locked in place at its end by aclamp 39 (40) with which the pulley 35 (36) is provided. A helicalspring 41 (42), secured at one end to pulley 35 (36) at a pointarcuately spaced from the clamp 39 (40), and at its other end to theouter face 45 of disc 21, keeps rope 31 (32) under tension.

An abutment means (not shown in FIG. 2) is provided on the face ofpulley 35 (36) which is directed towards disc 21, to engage acorresponding stop (only stop 71 being shown in FIG. 2 beneath thebroken- I away portion of the pulley 36) provided on the outer face 45of disc 21. This stop is arranged at a perdetermined position in orderto limit the extent of travel of pulley 35 (36) and the correspondingelongation of spring 41 (42) in response to the effect of centrifugalforce on the track 28 when the twisting unit 12 is operative.

In the illustrated stranding or cabling machine, the track 29 isprovided only for the purpose of counterbalancing track 28 duringoperation. Like the track 28, track 29 comprises two steel ropes 51 and52 which, stretched between the disc-shaped elements 20 and 21, pass inthe races of the two pulleys forming each of the pulley groups 25 and 27(FIG. 2 shows pulleys 53 and 54 of group 27, respectively, for ropes 51and 52), so that one end of each rope can be secured directly to theouter face 44 of disc20 and the other end of each rope engages the outerface 45 of disc 21 through'an elastic recovery mechanism for each rope,namely mechanism 67 for rope 51 and mechanism 68 for rope 52. As shownin the drawing the mechanisms 67 and 68 are similar to the mechanisms 47and 48 described above and a similar reference numeral convention isfollowed.

Each recovery mechanism 67 (68) of track 29 thus comprises, as in thecase of track 28, a race pulley 55 (56) pivoted at its center 57 (58).The rope 51 (52), whose terminal portion is carried in said race, islocked at its end to the pulley 55 (56) by the clamp 59 (60) with whichpulley 55 (56) isprovided. A helical spring 61 (62), secured at one endto pulley 55 (56) and at the other end to the outer face 45 of disc 21,keeps rope 51 (52) under tension.

An abutment means provided on the face of pulley 55 (56) which isdirected towards disc 21 is able to engage a corresponding stop providedon the outer face 45 of disc 21,to limit to a pre-established extent thetravel of pulley 55 (56) and the elongation of spring 61 (62) under theeffect of centrifugal force when the twisting unit 12 is operative. E16.3 shows only abutment means 63 provided on face 50 of pulley 56, forengaging stop 64, but it will be understood that similar abutment meansand stops are provided for the other pulleys 35, 36 and 55.

in a modified embodiment of the invention the ropes 31 and 32, 51 and 52could also be provided with recovery mechanisms at the other disc 20 forextension and recovery of the ropes at the outer faces 44 and 45 of bothdiscs 20 and 21.

The extension and recovery mechanisms 47, 48, 67, 68 can, of course, bedifferent from those of the currently preferred embodiment describedabove. In a further modification of the invention, each of saidextension and recovery mechanisms can, for instance, comprise a sliderslidable in appropriate guides, the slider being connected at one end toa helical spring, the other end of which spring is secured to the outerface of the corresponding disc. The travel of the slider can be limitedby an upper stop, with the length of the rope constituting the lowerlimit for the sliders travel.

Each pulley group 25 and 27 comprises only two pulleys, for example,pulleys 53 and 54 of group 27, but the pulley groups 24 and 26 comprisethree pulleys, namely two lateral pulleys, e.g., the pulleys 33 and 34of group 26, by which the two ropes 31 and 32 are deflected, as well asan intermediate pulley, shown at 43 in group 26. The intermediate pulley43 serves as a guide for the wire 30 to be twisted and is locatedbetween the pulleys 33 and 34. All three pulleys 33, 34 and 43 could beon a common shaft.

Bushes 46 are provided around the track 28 at appropriately spacedpositions to serve as a guide for the wires 30. The bushes 46 also actas spacing elements to keep constant the distance between the ropes 31and 32. Analogous spacing elements 49 are provided around the track 29.If necessary, said bushes 46, and for symmetry also the bushes 49, couldbe replaced by a flexible hose, appropriately connected to the ropes.

The hollow shaft 14 has a cylindrical cavity 65 coaxial with the shaft14. The wire-engaging circumferential surface of the deflecting pulley23 is aligned with the cavity 65 to receive wire approaching the pulley23 through the cavity 65. The disc is also provided with a cylindricalcavity therethrough (not shown) aligned with the wire receiving surfaceof the deflecting pulley 22.

Between disc 20 and disc 21 there is a rocking cradle 66, schematicallyshown in FIG. 1, upon which are mounted a take-up reel 72 for twistedwire and deflecting pulleys 69 and 70. ln a stranding or cabling machineof the outer take-up" type otherwise corresponding to the inner take-upmachine of the preferred embodiment shown in the drawing, the cradle 66would house the wire supplying reels instead of the take-up reel.

Operation The wires 30 to be twisted or stranded are arranged, while themachine is in restcondition, by unwinding them from supply reels (notillustrated) disposed outside the twisting unit 12. The wires are causedto advance in the direction of the arrow F in FIG. 1 along a paththrough the central cavity 65 of the shaft 14 to the deflecting pulley23, over the pulley 43, through bushes 46, over the intermediate pulleyof the pulley group 24, over the deflecting pulley 22, through thecylindrical cavity of the disc 20, over the pulleys 69, pulley 70, andare then anchored to reel 72.

When the twisting unit 12 is in rest condition, namely when thecentrifugal force is not acting and therefore the machine is at astandstill, the tracks 28 and 29 are stretched flat under tension, sincethe springs 41, 42 and 61, 62 respectively belonging to the recoverymechanisms 47, 48 and 67, 68, recover any excess portion of the ropes bywhich the length of the ropes forming the tracks exceeds the distancebetween discs 20 and 21.

When the twisting unit is started, and while its rotation speed isprogressively increasing, the springs 41, 42 and 61, 62 of the elasticrecovery mechanisms 47, 48 and 67, 68 elongate gradually, so that thetracks 28 and 29 continuously change their configuration in re sponse tothe increase of the centrifugal forces. This extension of the tracksstops when the pulleys 35, 36 and 55, 56, forming part of the recoverymechanisms have rotated to a point at which the abutment means providedon the pulleys is brought into contact with the stop provided on thediscs. At this moment, the ropes have reached a configuration 28a, 29a,which remains constantas long as the machine works under normal serviceconditions.

When the twisting unit 12 is operating, the wires 30, which advance witha translatory motion only through the cylindrical cavity 65 of thehollow shaft 14, are subjected to a first twist at the pulley 23, wherethey are compelled to twisting movement by the rotational motiontransmitted tothe pulley 23 by the rotating shaft 14. Y

The wires, simply stranded in this way, pass on to the pulley 43 and,through the bushes 46 of track 28, are conveyed to the intermediatepulley of group 24 and then to the deflecting pulley 22. After passingover the pulley 22 the wires 30 pass through the cylindrical cavitythrough disc 20 and are wound up on the winding drum or reel 72 mountedon the cradle 66. Since the cradle 66 and take-up reel 72 do not takepart in the rotation of the twisting unit 13, the wires are subjected toa second twist between the pulley 22 and the pulley 69.

A remarkable advantage afforded by the above illustrated twisting unitresides in the fact that, because the tracks 28 and 29 are perfectlyflexible, the configuration 28a and 29a taken spontaneously during theoperation is just that required by the centrifugal forces evolved byrotation. The only stresses generated in the steel ropes constitutingthe transfer tracks are mere tension stresses which can be easilycalculated, and consequently any possibility age is eliminated.

Numerous obv'iousmodifications in the structure, parts and operation ofthe invention will obviously sug gest themselves to those skilled in theart and such modifications are within the spirit and scope of thisinvention.

What is claimed is:

, 1. In a wire stranding machine having a twisting unit comprising apair of twisting means rotatable about a predeterminedaxis for receivingand twisting a plurality of wires, said twisting means being spaced fromeach other in the direction of said axis, and means for supplying saidwires to and receiving stranded wires from said pair of twisting means,the combination therewith of at least a pair of flexible track meansextending between said twisting'means, one of said track means beingdisposed to guide said wires from one of said twisting means to theother thereof and being disposed at one side of and in spaced relationto said axis and the other of said track means being disposed at theopposite side and in spaced relation to said axis, means for securingone end of each of said tracks at one end to one of said twisting means,means for securing the opposite end of each of said tracks to the otherof said twisting means for rotation of said tracks around said axis,said tracks being free intermediate their ends to move outwardly withrespect to said axis under the centrifugal forces to which they aresubjected during said rotation thereof, and elastic means urging saidtracks of ruptures or other daminwardly and toward said axis andlimiting the outward movement of said tracks. I

2. A wire stranding machine as set forth in claim 1, wherein at leastone of said tracks comprises a pair of metal ropes in side by-siderelation and further comprising means for guiding said wires along saidropes and for maintaining said ropes in spaced relation to each other.

3; A wire stranding machine as set forth in claim 2, wherein saidlast-mentioned means comprises a plurality of bushes extending aroundeach of said ropes, said bushes being spaced lengthwise of said ropesand having openings therethrough for receiving said wires.

4. A wire stranding machine as set forth in claim 1, wherein saidelastic means comprises at one end of each track means, a tensionapplying member movably mounted on one of said twisting means and meansfor securing the track means to said member, an elastic member actingbetween said tension applying member and said one twisting means to urgesaid tension applying member in a first direction which tends toelongate the track means and stop means for limiting movement of saidtension applying member in a second opposite direction.

5. A wire stranding'machine as set forth in claim 4, wherein saidtension applying member comprises a pulley rotatably mounted on thetwisting means and having a race receiving the track means, said elasticmember is spring means acting between the twisting means and said pulleyto urge said pulley to rotate in a direction which tends to elongate thetrack means and said stop means comprises an abutment on said pulleyengageable with a portion of the twisting means.

6. A wire stranding machine as set forth in claim 1, Q

wherein said twisting means comprises a pair of rotatwardly thereof,first guide means mounted on said one shaft and spaced outwardly fromsaid axis for receiving said wires from said opening and supplying saidwires to one end of one of said track means, said first guide meansbeing rotatable around said axis by saidone shaft, second guide meansmounted on the other of said shafts and spaced outwardly from said axisfor receiving said wires from the other end of said last-mentioned oneof said track means, said second guide means being rotable around saidaxis by said other shaft and further comprising means for receiving saidwires from said second guide means.

v7. A wire stranding machine as set forth in claim 6, wherein at leastone of said tracks comprises a pair of metal ropes in side-by-siderelation and further comprising means for guiding said wires along saidropes and for maintaining said ropes in spaced relation to each other.

8. A wire stranding machine as set forth in claim 7, wherein saidelastic means comprises a tension apply ing member movably mounted onone of said shafts for rotation therewith, means for securing the endsof said ropes nearer said one shaft to said member, spring means actingon said member in a direction which tends to elongate said ropes andstop means for limiting movement of saidmember in the oppositedirection.

1. In a wire stranding machine having a twisting unit comprising a pairof twisting means rotatable about a predetermined axis for receiving andtwisting a plurality of wires, said twisting means being spaced fromeach other in the direction of said axis, and means for supplying saidwires to and receiving stranded wires from said pair of twisting means,the combination therewith of at least a pair of flexible track meansextending between said twisting means, one of said track means beingdisposed to guide said wires from one of said twisting means to theother thereof and being disposed at one side of and in spaced relationto said axis and the other of said track means being disposed at theopposite side and in spaced relation to said axis, means for securingone end of each of said tracks at one end to one of said twisting means,means for securing the opposite end of each of said tracks to the otherof said twisting means for rotation of said tracks around said axis,said tracks being free intermediate their ends to move outwardly withrespect to said axis under the centrifugal forces to which they aresubjected during said rotation thereof, and elastic means urging saidtracks inwardly and toward said axis and limiting the outward movementof said tracks.
 2. A wire stranding machine as set forth in claim 1,wherein at least one of said tracks comprises a pair of metal ropes inside-by-side relation and further comprising means for guiding saidwires along said ropes and for maintaining said ropes in spaced relationto each other.
 3. A wire stranding machine as set forth in claim 2,wherein said last-mentioned means comprises a plurality of bushesextending around each of said ropes, said bushes being spaced lengthwiseof said ropes and having openings therethrough for receiving said wires.4. A wire stranding machine as set forth in claim 1, wherein saidelastic means comprises at one end of each track means, a tensionapplying member movably mounted on one of said twisting means and meansfor securing the track means to said member, an elastic member actingbetween said tension applying member and said one twisting means to urgesaid tension applying member in a first direction which tends toelongate the track means and stop means for limiting movement of saidtension applying member in a second opposite direction.
 5. A wirestranding machine as set forth in claim 4, wherein said tension applyingmember comprises a pulley rotatably mounted on the twisting means andhaving a race receiving the track means, said elastic member is springmeans acting between the twisting means and said pulley to urge saidpulley to rotate in a direction which tends to elongate the track meansand said stop means comprises an abutment on said pulley engageable witha portion of the twisting means.
 6. A wire stranding machine as setforth in claim 1, wherein said twisting means comprises a pair ofrotatable shafts mounted with their axes co-axial with said axis andspaced from each other in the direction of said axis, at least one ofsaid shafts having an opening therein at least a portion of whichextends axially thereof for feeding said wires therethrough andoutwardly thereof, first guide means mounted on said one shaft andspaced outwardly from said axis for receiving said wires from saidopening and supplying said wires to one end of one of said track means,said first guide means being rotatable around said axis by said oneshaft, second guide means mounted on the other of said shafts and spacedoutwardly from said axis for receiving said wires from the other end ofsaid last-mentioned one of said track means, said second guide meansbeing rotable around said axis by said other shaft and furthercomprising means for receiving said wires from said second guide means.7. A wire stranding machine as set forth in claim 6, wherein at leastone of said tracks comprises a pair of metal ropes in side-by-siderelation and further comprising means for guiding said wires along saidropes and for maintaining said ropes in spaced relation to each other.8. A wire stranding machine as set forth in claim 7, wherein saidelastic means comprises a tension applying member movably mounted on oneof said shafts for rotation therewith, means for securing the ends ofsaid ropes nearer said one shaft to said member, spring means acting onsaid member in a direction which tends to elongate said ropes and stopmeans for limiting movement of said member in the opposite direction.